Introduction. Modular junctions in total hip replacement (THR) have been a primary source of fretting and corrosion which can lead to implant failure. Fretting is a result of unintended micromotion between the femoral head and stem tapers and is suspected to result after improper taper seating during assembly. Two design factors known to influence in-vitro taper assembly mechanics are relative taper alignment—mismatch angle—and the surface finish—micro-grooves. However, these factors have not been systematically evaluated together. Objective. The objective of this study was to employ a novel, micro-grooved finite element (FEA) model of the hip taper interface and assess the role of taper mismatch angle and taper surface finish—smooth and rough—on the modular junction mechanics during assembly. Methods. A two-dimensional, axisymmetric model of a CoCrMo femoral head taper and Ti6Al4V stem taper was created using median measurements taken from over 100 retrieved implants. Micro-grooves on the stem and head taper were modeled using a sinusoidal function with amplitude and period corresponding to median retrieval measurements. To evaluate effects of a “smooth” head taper surface finish, additional models were run with a head taper having a flat edge (no micro-grooves). Lastly, mismatch between the stem and head taper was varied between distal-locked, no mismatch, and proximal-locked. To simulate assembly during surgery, boundary conditions were applied to move the femoral head taper at a constant velocity onto the stem taper until a 4kN reaction load was achieved. Models were assembled and meshed in ABAQUS Standard (v 6.17) using four-node linear hexahedral, reduced integration elements. Contact was modeled between the stem and head taper using surface-to-surface formulation with penalty contact and a coefficient of friction of 0.2. Forty simulations (5 mismatch angles x 2 head taper surface types x 4 stem taper surface finishes) were run. Outcome variables included contact area, contact pressure, equivalent plastic strain, and number of micro-grooves undergoing plasticity. Results. As expected, taper mismatch angle drove the location of contact to the distal or proximal ends. Increasing taper mismatch led to significant decreases in contact area for both micro-grooved and flat head taper models (Figure 1A). Taper mismatch had minimal effects on contact pressure (∼2.15 GPa) with the “rough” head taper surface finish but influenced the range of contact pressures (1.30 – 1.91 GPa) in the “smooth” head taper models (Figure 1B). Stress at the micro-grooves varied depending on the stem taper surface finish (Figure 2). Significant plastic deformation of the micro-grooves was only found in models with the “rough” head taper surface finish. Conclusion. Regardless of the taper surface finish, contact area decreased by 30% – 58% when going from a 3’ – 12’ mismatch. Reduced contact area may significantly influence the long-term stability of the implant. Modeling the taper micro-grooves led to plastic deformation consistent with those found from retrieved implants—indicating the importance of modeling the surface finish of tapers. These models will be used to identify the optimal design factors to maximize stability of the modular taper junctions. For any figures or tables, please contact authors directly

Introduction. The release of metallic debris can promote many adverse tissue reactions, as metallosis, necrosis, pseudotumors and osteolysis . 1–3. This debris is mainly generated by the fretting-corrosion mechanism due to the geometric difference in the head-stem interface . 4. Retrieval and in silico analysis showed the roughness of the stem-head interface appears to play an important role in the volume of material lost and THA failure . 5–7. The technical standard ISO 7206-2 recommends the measurement of average roughness (Ra) and max height of the profile (Rz) to control the quality of the surface finish of articulating surfaces on THA implants. However, despite the importance of the trunnion roughness, there is no specific requirement for this variable on the referred technical standard. The present study carried out a surface finish analysis of the trunnion of hip stems from five distinct manufacturers. Methods. Four stems (n = 4) from five (5) distinct manufacturers (A, B, C, D, and E) were used to evaluate the roughness of the trunnion. All the stems are similar to the classical Exeter stem design, with a 12/14 taper and a polished body surface. The roughness of trunnions was evaluated according to ISO 4287 and ISO 13565-2. The total assessment length was 4.8 mm with 0.8 mm cut-off. The first and last 8.33% of assessment length were not considered. The measurements of all samples were made in a rugosimeter with 2 µm feeler ITP (Völklingen, Germany), the velocity of 0.5 mm.s. -1. , and a force of 1.5 mN. The calibration was made at 20 ºC and relative humidity at 50%. The Kruskal Wallis with post hoc Nemenyi test was used to evaluate the difference of Ra among the manufacturers. The confidence level was set at 5%. Results and Discussion. The analysis of surface finish revealed different roughness among the manufactures (p < 0.005), with Ra between 0.061 µm to 3.184 µm and Rz varying of 0.41 µm to 12.69 µm. The manufacturers A and E had a Ra (2.587±0.050 µm and 3.146±0.031µm) of the trunnion similar to founded by Panagiotidou et al (2013). Within such range, the trunnion has shown a high presence of pit . 8. The manufacturer C, on the other hand, had the best surface finish of the trunnion (Ra = 0.069±0.010 µm and Rz = 0.505 ± 0.076 µm). This more smooth surface might increase the taper strength, reduce the shear stress and the susceptibility to the fretting-corrosion damage . 4,8. . Conclusion. The results were worrying because there is great variability of roughness among the manufacturers with the occurrence of trunnions with roughness too high. Nevertheless, the ISO technical standard does not recommend any procedure or minimum parameters acceptable for the surface finish of the trunnion. The revision of ISO 7206-2 would guarantee better control of trunnion roughness to reduce the amount of metallic debris and increase the safety of THA implants. Additional research is needed to determine a target value for this variable. For any figures or tables, please contact authors directly

The effects of wear particles on artificial hip joints are well documented. Aseptic loosening has been demonstrated to be dependent on both particle numbers and particle size. This study investigated the effects of stem material and surface finish on particles produced at the stem/cement interface in cemented artificial hips. Three commonly used implant materials of different hardness were investigated: cobalt chrome, the hardest of the three materials, stainless steel and titanium alloy which was the softest material tested. The surfaces of three femoral stems with different surface finishes were measured and used as templates; the Exeter which is highly polished, the Charnley which is moderately rough and the Capital which is very rough. Test plates were manufactured in each material and with each surface finish making 9 sets of plates in all. The plates were opposed to cement pins (CMW) in a sliding wear tester. The volume of debris produced was calculated from measurements of the pins pre- and post-test. The debris was collected, filtered and examined under the electron microscope, which allowed particle sizes of a representative sample of debris to be measured. From this mean particle size was calculated. Volume of debris: for all three materials the roughest surface produced the greatest volume of debris and the smoothest surface the least. For any given surface finish the softest material produced the greatest volume of debris and the hardest material the least. Size of particles: for all three materials the roughest surfaces produced the largest particles and the smoothest surface the smallest particles. For any given surface finish the hardest material produced the smallest particles and the softest material produced the largest particles

Introduction:. There has been widespread concern regarding the adverse tissue reactions after metal-on-metal (MoM) total hip replacements (THR). Concerns have also been expressed with mechanical wear from micromotion and fretting corrosion at the head/stem taper junction in total hip replacements. In order to understand the interface mechanism a study was undertaken in order to investigate the effect of surface finish and contact area associated with modular tapers in total hip replacements with a single combination of materials of modular tapers. Methods:. An inverted hip replacement setup was used (ASTM F1875-98). 28 mm Cobalt Chrome (CoCr) femoral heads were coupled with either full length (standard) or reduced length (mini) 12/14 Titanium (Ti) stem tapers. These Ti stem tapers had either a rough or smooth surface finish whilst all the head tapers had a smooth surface finish. Wear and corrosion of taper surfaces were compared after samples were sinusoidally loaded between 0.1 kN and 3.1 kN for 10 million cycles at 4 Hz. In test 1 rough mini stem tapers were compared with rough standard stem tapers whilst in test 2 rough mini stem tapers were compared with smooth mini stem tapers. Surface parameters and profiles were measured before and after testing. Electrochemical static and dynamic corrosion tests were performed between rough mini stem tapers and smooth mini stem tapers under loaded and non-loaded conditions. Results:. In test 1 following the mechanical loading test the surface roughness parameters on the head taper were significantly increased when they were coupled with the mini stem tapers compared to the standard stem tapers (p = 0.046). Similarly in test 2 the surface roughness parameters on the head tapers were significantly increased when mini rough stem tapers were used compared to smooth mini stem tapers (p = 0.04). Corrosion testing showed breaching of the passive film on the rough but not the smooth neck tapers. Conclusion:. This study has identified enhanced fretting corrosion at the modular taper junction associated with roughened surface finish and small neck tapers and points to the overall concern associated with the use of modular taper connections in orthopaedic implants. Crevice corrosion is identified as the predominant mechanism, with evidence of pitting in all rough mini neck tapers. The greatest wear and corrosion was in the plane where the greatest bending moments were generated, implicating fretting as a mechanism. The rough mini neck tapers have a reduced surface area at the interface and ultimately bending forces are concentrated here

The advantages of modularity in both primary and revision hip surgery are well documented, and have been at the heart of innovation in hip implant design over the last two decades. Modularity allows us to address version, length and offset issues and to restore optimal hip biomechanics. There are, however, increasing clinical concerns associated with the failure of taper junctions. The use of large femoral heads and modular stems are now considered major risk factors for taper corrosion. I will summarise our laboratory and retrieval data on taper design and tribology in order to put in perspective the clinical use of modularity in hip arthroplasty. Modular junctions rely on a frictional interlock. The engagement obtained and resulting micromotion is strongly influenced by taper size, taper length/engagement, material, surface finish, neck length and offset. In our quest for thinner femoral necks, greater offsets and bigger femoral heads, we have inadvertently created an environment that can generate fretting corrosion at modular junctions and leads to premature implant failure. An inverted hip replacement setup was used similar to the specified ASTM test (ASTM F1875–98). Twenty-eight millimeter Cobalt Chrome (CoCr) femoral heads were coupled with either full length (standard) or reduced length (mini) 12/14 Titanium (Ti) stem tapers. These Ti stem tapers had either a rough or smooth surface finish whilst all the head tapers had a smooth finish. Wear and corrosion of taper surfaces were compared following a 10 million loading cycle. The surface roughness parameters on the head taper were significantly increased when the head-stem contact area was reduced. Similarly, the surface roughness parameters on the head taper were significantly increased when rough stem tapers were used. With rough male tapers the CoCr head taper became circumferentially ridged with distinct areas of pitting corrosion similar to that seen on some retrievals. In these tests similar surface morphology to that on retrieved femoral heads was seen on the female head taper. Thirty-six millimeter CoCr femoral heads were also coupled with either a CoCr or Ti stem with 12/14 tapers all with smooth finish. Increasing perpendicular horizontal offsets in the sagittal plane created incremental increases in torque. A proportional relationship between torque and corrosion was observed for both CoCr-CoCr and CoCr-Ti material combinations. In-vitro studies were used to evaluate the role of: taper size, angle mismatch, surface finish, and manufacturing tolerances on taper engagement. In-vitro loading analysis was performed to determine the bearing friction experienced by the taper connection. The component materials analysed were CoCr and Ti for stem design and CoCr/CoCr, ceramicized metal/CoCr, and CoCr/Ti for head/neck tapers. The high performance combinations included tapers with larger diameters, rougher surface finish, tighter tolerances and a proximal locking location. Loading studies demonstrate a 15 – 31% reduction in frictional torque (for 28, 36 and 40mm head sizes) using the ceramicized metal/XLPE couples compared to CoCr/XLPE couples. Retrieval studies were conducted to assess taper corrosion using the Goldberg system and SEM analysis. Two hundred-nine taper surfaces, with in-vivo time varying from 1 week and 10 years, were analysed showing that ceramicized metal femoral heads have a lower corrosion score compared to CoCr femoral heads. Understanding the key design and surgical factors that drive the performance of taper junctions is vital for the surgical community. There is a body of knowledge that supports appropriate taper use / modularity to help surgeons deal with complex situations. We must be careful not throw the baby out with the bathwater

Introduction. There is considerable interest in the orthopaedic community in understanding the multifactorial process of taper fretting corrosion in total hip arthroplasty (THA). Previous studies have identified some patient and device factors associated with taper damage, including length of implantation, stem flexural rigidity, and head offset. Due to the complexity of this phenomenon, we approached the topic by developing a series of matched cohort studies, each attempting to isolate a single implant design variable, while controlling for confounding factors to the extent possible. We also developed a validated method for measuring material loss in retrieved orthopaedic tapers, which contributed to the creation of a new international standard (ASTM F3129-16). Methods. Based on our implant retrieval collection of over 3,000 THAs, we developed independent matched cohort studies to examine (1) the effect of femoral head material (metal vs. ceramic, n=50 per cohort) and (2) stem taper surface finish (smooth vs. microgrooved, n=60 per cohort). Within each individual study, we adjusted for confounding factors by balancing implantation time, stem taper flexural rigidity, offset, and, when possible, head size. We evaluated fretting and corrosion using a four-point semiquantitative score. We also used an out-of-roundness machine (Talyrond 585) to quantify the material loss from the tapers. This method was validated in a series of experiments of controlled material removal on never-implanted components. Results. In the first study, the ceramic cohort exhibited a 92% reduction in cumulative volumetric loss from both the head and neck taper surfaces compared to the CoCr cohort (p < 0.001). In the CoCr cohort, there was greater material loss from femoral head tapers as compared with stem tapers (p < 0.0001). There was also a correlation between visual scoring and volumetric material loss (ρ = 0.67, p < 0.01). In the second study, taper damage was not different between the smooth and microgrooved taper cohorts when evaluated at the head bore (p=0.14) or the stem tapers (p=0.35). There was also no difference in material loss between the most damaged CoCr heads in the two cohorts (p>0.05). Conclusions. Our findings suggest that fretting and corrosion damage and material loss from the stem taper are mitigated, and on the head taper, eliminated with the use of a ceramic vs. metal femoral head. We also found that fretting and corrosion damage was insensitive to differences in stem taper surface finish and the presence of microgrooves. Although visual scoring was effective for preliminary screening to separate tapers with no or mild damage from tapers with moderate to severe damage, it was not capable of discriminating within the large range of material loss observed at the taper surfaces with high fretting-corrosion scores. Thus, for moderate to severely damaged conical tapers, direct measurement is necessary. A drawback of a matched cohort approach is that a large retrieval collection is necessary to effectively match an investigational group of implants with an appropriate control cohort. Notwithstanding this limitation, the matched cohort approach has been an effective approach to study the complex multifactorial problem of taper fretting and corrosion

The advantages of modularity in both primary and revision hip surgery are well documented, and have been at the heart of innovation in hip implant design over the last two decades. There have been significant developments in modularity proximally at the head-neck junction, more distally with modular necks and at mid-stem level, notable for complex revisions. Modularity allows us to address version, length and offset issues and to restore optimal hip biomechanics. There are, however, increasing clinical concerns associated with the failure of taper junctions. The use of large femoral heads and modular stems are now considered major risk factors for taper corrosion. Recent studies have shown an 8–9% early revision rate of one modular neck design due to pain and adverse local tissue reaction. I will summarise our laboratory and retrieval data on taper design and tribology in order to put in perspective the clinical use of modularity in hip arthroplasty. Modular junctions rely on a frictional interlock. The engagement obtained and resulting micromotion is strongly influenced by taper size, taper length/engagement, material, surface finish, neck length and offset. In our quest for thinner femoral necks, greater offsets and bigger femoral heads, we have inadvertently created an environment that can generate fretting corrosion at modular junctions and leads to premature implant failure. Our work demonstrates that increasing torque and bending moment leads to increased susceptibility to fretting corrosion at the modular taper interface of total hip replacements. This is particularly relevant with the increasing use of larger diameter femoral heads that produce higher torques. It also identifies surface area and surface finish as important factors in wear and corrosion at the modular interface of total hip replacements. Critically, the combination of these factors can lead to extensive corrosion at the interface. Surgical technique is also important. Higher impaction loads on clean, dry surfaces result in greater contact length and extraction forces, which may influence micromotion. It is critical in future that all innovation is introduced in a systematic gradual fashion so that we do not fall into similar traps again. The unintended consequences of minor changes in design may have a massive effect on outcomes. Our findings suggest that it may be possible to continue to employ the advantages of modularity in hip surgery whilst avoiding some of the pitfalls that have led to the failure of some modular systems. Understanding the key design and surgical factors that drive the performance of taper junctions is vital for the surgical community. There is a body of knowledge that supports appropriate taper use / modularity to help surgeons deal with complex situations. We must be careful not throw the baby out with the bathwater

Introduction. Implant-cement debonding at the knee has been reported previously [1]. The strength of the mechanical interlock of bone cement on to an implant surface can be associated with both bone cement and implant related factors. In addition to implant surface profile, sub-optimal mixing temperatures and waiting times prior to cement application may weaken the strength of the interlock. Aims. The study aimed to investigate the influence of bone cement related factors such as mixing temperature, viscosity, and the mixing and waiting times prior to application, in combination with implant surface roughness, on the tensile strength at the interface. Materials and Methods. Tensile tests were carried out on two types of hand-mixed cement, high (HV) and medium viscosity (MV), sandwiched between two cylindrical Cobalt-Chrome coupons with either smooth (60 grit) or rough (20 grit) surface finishes. 144 Specimens were prepared with a cement thickness layer of 2.5 mm in customised rigs (Figure 1). The samples were grouped and tested at two mixing temperatures (23 and 19 degrees), at different mixing times (HV-30s, MV-45s). Waiting times after mixing were varied between early (1.5 min), optimal (4.5 min) or late (8 min); for HV and 4 min, 7.5 min and 11 min for MV cements. All the samples were cured for 24 hours prior to testing. The peak force and stress was calculated for all specimens. Results and Conclusion. Surface Finish: Rough surfaced samples had significantly higher (p < 0.05) mean tensile forces and stress than smooth samples at both 19 and 23 degrees across HV and MV cement types. Cement Type: MV cements, when applied to rough samples with waiting times of 4 minutes at 23 degrees, and 11 minutes at 19 degrees, resulted in the highest peak tensile forces, followed by 7.5 minutes at 23 and 19 degrees respectively (Figure 2). Temperature at different application times for rough and smooth samples: for MV cement, rough samples prepared at 23 degrees, 4 minutes, and smooth samples at 19 degrees, 7.5 minutes were found to be significantly better (p < 0.05) than their counterparts. For HV cement, 23 degrees was found to be better (p < 0.05) for smooth samples at applications times of 4.5 and 8 minutes and 19 degrees for application times of 1.5 minutes. No significant difference was noted for rough samples for the same. Application times at different temperatures for rough and smooth samples: at both 19 and 23 degrees, there were no differences between application times within the rough sample groups for HV or MV. However, for smooth samples, HV cement, tensile forces were significantly higher (p < 0.05) at 23 degrees in the following order; 8 minutes > 4.5 minutes > 1.5. The results show that implant surface roughness and cement mixing time, temperature, viscosity and application times affect the strength of the interlock at the interface

Orthopaedic implants, such as femoral heads, sockets and stems, are manufactured with a high degree of smoothness and very low form error in order to function as low wear bearings. The surfaces are subject to both wear and damage during in vivo use. Articulating surfaces naturally wear during normal use. Aseptic loosening associated with osteolysis and release of wear particles is the main reason for revision of total hip arthroplasty (THA). Damage of femoral heads is well known to increase the wear rate at the articulating surface and is vulnerable to scratching during the maneuver of positioning the femoral component into the acetabulum component either in primary as in revision total hip arthroplasties. The findings emphasize the importance of achieving and maintaining good surface finish of the femoral head component. The author presents a very simple and “zero cost” method of preventing scratching of the femoral head of any kind of total hip prosthesis (ceramic on ceramic, ceramic on poly, metal on metal, metal on poly and even metal on ceramic) when the reduction of the femoral head prosthesis is done inside the new acetabular component with metal, ceramic liner or poly liner with metal back (where the scratching can also occur) as one of the final stages of the surgical procedure which can be crucial to the long survival of the hip prosthesis. A short one minute video on an e-poster will show how this can be done being an easy, reproducible, safe and reliable technique to prevent femoral head scratching

Introduction. Large-scale retrieval studies have shown backside wear in tibial inserts is dependent on the surface roughness of the tibial tray. Manufacturers acknowledge this design factor and have responded with the marketing of mirror-finished trays, which are clinically proven to have lower wear rates in comparison to historically “rough” (e.g. grit blasted) trays. While the relationship between wear and surface roughness has been explored in other polymer applications, the quantitative dependence of backside wear rate on quantitative surface finish has not yet been established for modern devices. The present study evaluates small-excursion polyethylene wear on pucks of a variety of surface roughnesses. The objective of this study is to determine where inflection points exist in the relationship between surface roughness and wear rate. Materials and Methods. An AMTI Orthopod, 6-station pin on disk tribotest was designed to mimic worst-case in vivo backside wear conditions based on published retrieval analyses. Titanium (Ti6Al4V) pucks with six different surface roughness preparations (Sa ranges from 0.06 um to 1.06 um) were characterized with white light profilometry. Never implanted polyethylene tibial inserts (never irradiated, EtO sterilized) were machined into 6 mm diameter cylindrical pins. Fretting-type motion was conducted in a 2mm square pattern at 2Hz under 100 N constant force in 25% bovine serum lubricant for 1.35 million cycles in triplicate. Mass measurements were taken every 225 thousand cycles. Results. Over the range of surface roughness studied (Sa = 0.06 – 1.06 µm), wear rate grew logistically. The wear rate for highly polished titanium (Sa = 0.06 µm) was not statistically different from less-polished titanium with Sa of 0.14 µm (p > 0.1). Titanium pucks having the highest surface roughness (Sa > 0.5µm), removed material significantly faster than those with roughness less than 0.3µm. The results of these tests suggest that Ti trays with Sa less than 0.15µm may yield equivalent clinical backside wear results, while pucks with Sa greater than 0.15µm begin to have increased wear rates that may be clinically significant. The two pucks with Sa greater than 0.5 µm yielded wear rates failing to be statistically differentiable (p = 0.059), corresponding with the flattening of the logistic curve. Discussion. These results suggest that baseplates with Sa less than 0.15 µm may ultimately yield clinically equivalent outcomes. The wear rate curve changes slope between Sa 0.14 and 0.22 µm and continues to increase across the range of surface roughnesses studied. The wear rates on rough pucks (Sa > 0.5 µm) showed high variation, reducing the ability to distinguish the two statistically (p = 0.059). Further study will better distinguish wear properties at higher surface roughnesses. Conclusion. These findings demonstrate that there may be a range of finishes between a mirror polish and grit blast that may produce clinically equivalent wear rates. This work provides justification for further study into the relationship between backside wear, baseplate tray roughness, and material choices. For any figures or tables, please contact authors directly

Introduction. Wear of polyethylene tibial inserts has been cited as being responsible for up to 25% of revision surgeries, imposing a very significant cost burden on the health care system and increasing patient risk. Accurate measurement of material loss from retrieved knee bearings presents difficult challenges because gravimetric methods are not useful with retrievals and unworn reference dimensions are often unavailable. Geometry and the local anatomy restrict in vivo radiographic wear analysis, and no large-scale analyses have illuminated long-term comparative wear rates and their dependence on design and patient factors. Our study of a large retrieval archive of knee inserts indicates that abrasive/adhesive wear of polyethylene inserts, both on the articular surface and on the backside of modular knees is an important contributor to wear, generation of debris and integrity of locking geometry. The objective of the current study is to quantify wear performance of tibial inserts in a large archive of retrieved knees of different designs. By assessing wear in a large and diverse series, the goal is to discern the effect on wear performance of a number of different factors: patient factors that might help guide treatment, knee design factors and bearing material factors that may inform a surgeon's choice from among the array of arthroplasty device options. Methods. An IRB approved retrieval database was queried for TKA designs implanted between 1997 and 2017. 1385 devices from 5 TKA designs were evaluated. Damage was ranked according to Hood's method, oxidation was determined through FTIR, and wear was determined through direct measurement of retrieved inserts using a previously established protocol. Design features (e.g. materials, conformity, locking mechanisms, stabilization, etc.) and patient demographics (e.g. age, weight, BMI, etc.) were cataloged. Multivariate analysis was performed to isolate factors contributing to wear, oxidation, and damage. Results. Wear and oxidation were both found to scale with time in vivo in conventional and crosslinked polyethylene. Wear rate was also found to scale with time in vivo, but was not found to be a function of oxidation. Regression shows patient age and female sex to correlate negatively with wear rate. Polished trays, crosslinked polyethylene, and constrained knee designs are all correlated with decreased wear rates. Discussion. While this study indicates that loosening and infection are predominant causes for TKA revision, wear related failure remains common. We believe this to be the largest existing comparative study of modern TKA wear rates. Insert wear is shown to correlate with several patient factors. Wear performance also varies significantly between knee designs, polyethylene material choice and tray surface finish. When compared to a historical standard for knee wear rates, all designs evaluated in the current study exhibited significant improvements in wear rates. Retrieval analysis can provide insight into implant and patient related factors that contribute to knee wear, with the goal of improving patient outcomes and best matching design decisions to patient populations

Introduction. Implant associated infections are responsible for over 10 % of recorded orthopaedic revision surgeries across the UK, with higher infection rates commonly observed for other endoprostheses such as cranioplasties. To prevent colonization and biofilm formation on implant surfaces, the use of silver coatings has shown positive results in clinical setting due to its synergistic function with conventional antibiotic prophylaxes. Additive manufacturing allows manufacture of entirely new implant geometries such as lattice structures to enhance osseointegration, however this limits the ability to uniformly coat implants. Direct integration of silver into the powder feedstock for selective laser melting (SLM) may allow manufacture of a biomedical alloy with innate, long lasting antimicrobial properties without compromising possible geometries and with no coating process necessary. Methods. Feedstock powders of 15–45 micron Grade 5 Ti-64 (Renishaw Plc) and Ag-999 powder (CooksonGold) were characterized using laser particle size analysis, ICP-OES, LECO-ONH, and morphological analysis in SEM. A blend of Ti-64 with 3 wt% Ag-999 powder (Ti-643) was produced by tumble blending, and validated by SEM and EDS. Parameters for manufacture were established using a 17 point design of experiment (DoE) exploring a 2D parameter space of applied laser power and laser scanning speed. Samples were manufactured using a ConceptLaser M2 LaserCusing SLM. Density was assessed by He pycnometry, and cross-sections analysed for defects by optical microscopy. Silver distribution was mapped by micro X-Ray Fluoroscopy (µXRF) and energy-dispersive X-ray spectroscopy (EDS). Optimum parameters were identified and used to manufacture all subsequent samples. Cylindrical Ti-643 samples were manufactured for further physical characterization and bacterial investigation, alongside control Ti-64 samples manufactured using existing optimum parameters. Samples were polished using silicon carbide papers to a 4000-grit surface finish. Contact angle measurements were made by goniometry. Silver elution characteristics were assessed by immersion in water refreshed on a daily basis, and sampled over a 14 day period using ICP-OES. Viability of S. aureus was compared to control samples according to the Japanese standard test method, JIS Z 2801:2000. Results. Across the entire parameter space tested, selective laser melting (SLM) of all 17 samples was successful, with no delamination. An increased recoater blade speed was required to achieve uniform spreading in process versus pure Ti-6Al- 4V powder, indicating an increased cohesivity of the Ti-643 blend. The presence of silver in all samples was confirmed by µXRF, indicating that there was no excessive evaporation of silver in-process. Laser parameters were found to alter the defect density and microstructure scale, though sample density was tightly clustered in a range from 4.415 to 4.453 gcm-3, showing relatively low process variation. No significant difference in bacterial survival was found between control and Ti-643 samples, indicating that further microstructural optimization is needed to guarantee efficacy

Shortened humeral stem implants can be advantageous as they preserve more of the patient's bone and are not limited by the canal for placement in the proximal body. However, traditional longer stems may help stabilize the implant through interaction with the dense cortical bone of the canal. We developed an FEA model to gage the contributions of design features such as stem length, coatings, and interference fit. Models were constructed in FEMAP and solved using the NX Nastran advanced nonlinear static solver. The Turon (DJO Surgical) implant geometry was imported from a Solidworks CAD file and bone geometry was taken from a statistical shape model by Materialise representing the mean humeral geometry of 95 healthy humeri (avg age = 69.9 years). Implant and cancellous bone were considered to be linear homogeneous materials, and the cortical shell was modeled as orthotropic. Interference fits between the implant and cancellous bone surfaces were modeled using the gap feature of NX Nastran with friction coefficients corresponding to the surface finish. Loading was applied through a control node located at the center for the replacement head. Two loading conditions were analyzed, one representing torsion about the neck axis with a magnitude of 3140 Nm and one representing the peak load vector during activities of daily living. Using resection plane nodes at the intersection of the implant and bone, the histograms of micromotion and the associated 5. th. , 50. th. , and 95. th. percentile values were calculated. For a traditional length stem, the dominate effect on the predicted micromotion at the resection plane was the interference fit in the coating region. The contribution of a traditional length stem to resection plane micromotion was complex and depended on the presence of the stem and the amount of interference fit in the coating region

Outcomes of THA after Hip Arthroscopy. Hip Injections and Rapidly Progressing Joint Degeneration. Procedure Duration Wound Complications & LOS. Losing Weight Following TKA and its Influence on Outcome. Radiographic Severity of Arthritis & Patient Satisfaction in TKA. Intra-wound Vancomycin Powder Reduces Infections in TJA. Increased Non-stemmed Tibial Failures with BMI ≥ 35. Influence of Component Alignment on Outcome in Varus TKA. New TKA Designs - Do Patients Notice?. Bariatric Surgery Prior to TKA Associated with Fewer Complication. Metal Sensitivity Correlates with Pain in Patients with TJA. Blood Culture Bottles vs. Swabs for Microbial Detection in PJI. I&D Prior to 2 Stage Revision TKA Doesn't Increase Risk of Failure. Outpatient Total Joint Leads to Substantial Burden of Phone Calls. Wear and lysis of HXL Sockets: Effect of Head Size @ 10–14 Years. Surface Finish & Survivorship of Cemented Stems in THA. Patient Reported Outcome as a Tool for Appropriateness in THA. Neuraxial Anesthesia and Post-op Complications and Transfusions

Total knee arthroplasty (TKA) is reliable, durable, and reproducible in relieving pain and improving function in patients with arthritis of the knee joint. Cemented fixation is the gold standard with low rates of loosening and excellent survivorship in several large clinical series and joint registries. While cementless knee designs have been available for the past 3 decades, changing patient demographics (i.e. younger patients), improved implant designs and materials, and a shift towards TKA procedures being performed in ambulatory surgery centers has rekindled the debate of the role of cementless knee implants in TKA. The drive towards achieving biologic implant fixation in TKA is also driven by the successful transition from cemented hip implants to uncemented THA. However, new technologies and new techniques must be adopted as a result of an unmet need, significant improvement, and/or clinical advantage. Thus, the questions remain: 1) Why switch; and 2) Is cementless TKA more reliable, durable, or reproducible compared to cemented TKA?. There are several advantages to using cement during TKA. First, the technique can be universally applied to all cases without exception and without concerns for bone health or structure. Second, cement can mask imprecisions in bone cuts and is a remarkably durable grout. Third, cement allows for antibiotic delivery at the time surrounding surgery which has been shown in some instances to reduce the risk of subsequent infection. Finally, cement fixation has provided successful and durable fixation across various types knee designs, surface finishes, and articulations. On the other hand, cementless knee implants have had an inconsistent track record throughout history. While some have fared very well, others have exhibited early failures and high revision rates. Behery et al. reported on a series of 70 consecutive cases of cementless TKA matched with 70 cemented TKA cases based on implant design and demographics and found that cementless TKA was associated with a greater risk of aseptic loosening and revision surgery at 5 years follow up. Finally, to date, there has not been a randomised controlled clinical trial demonstrating superiority of cementless fixation compared to cemented fixation in TKA. Improvements in materials and designs have definitely made cementless TKA designs viable. However, concerns with added cost, reproducibility, and durability remain. Cement fixation has withstood the test of time and is not the main cause of TKA failure. Therefore, until there is significant data showing that cementless TKA is more durable, reliable, and reproducible compared to cemented TKA, the widespread use of these implants cannot be recommended

The technique involves impaction of cancellous bone into a cavitary femur. If segmental defects are present, the defects can be closed with stainless steel mesh. The technique requires retrograde fill of the femoral cavity with cancellous chips of appropriate size to create a new endomedullary canal. By using a set of trial impactors that are slightly larger than the real implants the cancellous bone is impacted into the tube. Subsequent proximal impaction of bone is performed with square tip or half moon impactors. A key part of the technique is to impact the bone tightly into the tube especially around the calcar to provide optimal stability. Finally a polished tapered stem is cemented using almost liquid cement in order to achieve interdigitation of the implant to the cancellous bone. The technique as described is rarely performed today in many centers around the world. In the US, the technique lost its interest because of the lengthy operative times, unacceptable rate of peri-operative and post-operative fractures and most importantly, owing to the success of tapered fluted modular stems. In centers such as Exeter where the technique was popularised, it is rarely performed today as well, as the primary cemented stems used there, rarely require revision. There is ample experience from around the globe, however, with the technique. Much has been learned about the best size and choice of cancellous graft, force of impaction, surface finish of the cemented stem, importance of stem length, and the limitations and complications of the technique. There are also good histology data that demonstrate successful vascularization and incorporation of the impacted cancellous bone chips and host bone. Our experience at the clinic was excellent with the technique as reported in CORR in 2003 by M Cabanela. The results at mid-term demonstrated minimal subsidence and good graft incorporation. Six of 54 hips, however, had a post-operative distal femoral fracture requiring ORIF. The use of longer cemented stems may decrease the risk of distal fracture and was subsequently reported by the author after reviewing a case series from Exeter. Today, I perform this technique once or twice per year. It is an option in the younger patient, where bone restoration is desired. Usually in a Paprosky Type IV femur, where a closed tube can be recreated and the proximal bone is reasonable. If the proximal bone is of poor quality, then I prefer to perform a transfemoral osteotomy, and perform an allograft prosthetic composite instead of impaction grafting, and wrap the proximal bone around the structural allograft. I prefer this technique as I can maintain the soft tissues over the bone and avoid the stripping that would be required to reinforce the bone with struts or mesh. Another indication for its use in the primary setting is in the patient with fibrous dysplasia

Introduction. Cementless devices can be designed with varying surface treatments with the hope of achieving osseointegration. The surface finish dictates the interaction, adhesion and growth of bone therefore it is an important parameter that be measured and compared. The surface topography of a material can be viewed both microscopically and macroscopically. Surface microtopography focuses on the peaks and valleys where deviations in the characteristics of the size and spacing of these features determine the variability between surface topography. The most common parameter used worldwide to describe surface roughness is the arithmetic average height (Ra). The definition of Ra is the absolute deviation of the surface irregularities from a mean line across the sampling length given by the equation shown in figure 1. Many techniques can be used to relate to surface characteristics of materials, with the common two options revolving around contact and non-contact methods. These techniques are expensive and are limited in detecting the interaction of implantable devices at a macroscopic level. This study sought to develop a method to determine the surface roughness and characterise implants based on cross sectional images and scanning electron microscopy. Method. The profile of 6 trunnions from a total hip replacement was obtained in x and y coordinates along a set length using a profilometer. A custom program to calculate the Ra of the material was created using a mathematical program (MATLAB). Each material profile was inputted into a mathematical program to provide the surface roughness of the material. The surface parameters were initially obtained from a surface analyser to determine the accuracy of the program. Results. The mean difference in the Ra measurements was 0.2μm ± 0.01μm. Conclusion. This study has shown that the roughness parameters of a material obtained using the custom program was within acceptable variation to the results from the profilometer. This is indicative of the program functioning as required. The surface characteristics of implantable devices are important factors which can influence cellular behaviour hence adhesion which directly correlate to the interaction with bone. Therefore having a method to determine the surface roughness is a vital tool, which can provide insight on the inherent topography

The most recent Australian registry has a database of 547,407 knee arthroplasties, having added over 52,000 in 2016. Total knee arthroplasties (TKA) comprise 83.8%, revisions (RevTKA) 8.1% and “partials of all types” 8.1%. Since 2003, the percent of TKA has increased from 76.7%, RevTKA has stayed stable and partial replacements have declined from 14.5%. In the last year, however, TKA declined slightly. There is a slightly higher percentage of women (56.1%) undergoing TKA and this has remained very stable since 2003. Revision rates are slightly higher for men. Percentages of the youngest (<55) and oldest (>85) are small and stable. The 75–84 year olds have declined as 55–74 year olds have increased. This represents a gradual shift to earlier TKA surgery. More patella are resurfaced and this is a gradual trend with a cross over in 2010 when half were resurfaced. Computer navigation is progressively more popular and now accounts for almost 30% of cases. Cement fixation is also increasing and accounts for about 65% of cases. Crosslinked polyethylene is gradually replacing non crosslinked and in 2014 was used in 50% of cases. Revisions are performed most commonly for loosening and infection. Revision rates correlate directly with age. Loosening is the most common indication for revision in both genders, but males have a distinctly higher revision rate due to infection. Revision rates are slightly higher in all forms of mobile bearing than fixed bearing. Minimally constrained (cruciate retaining) devices are used in the majority of TKAs. Posterior stabilised implants are in slight decline, having peaked in about 2008–2010. Minimally constrained implants are in slight decline as medial pivot/medial congruent devices have been used more frequently. Revision rates are similar amongst all three implant types: PS implants are revised at a slightly higher rate. When an early Medial Pivot (MP) implant is excluded the newer version has better results. The reasons for revision are similar amongst all 3 groups with slightly higher loosening rates for PS designs. (Could this represent backside wear with older locking mechanisms, surface finish and non crosslinked poly?) The MP designs had slightly higher revision rates for “pain”, which is not recognised as a reasonable indication for revision. Revision rates are steadily higher for TKAs without patella resurfacing over 16 years, but the questions as to whether: i. the surgeries were secondary resurfacings or full revisions or ii. if secondary resurfacings eliminated pain are unknown. The combinations at greatest risk of revision were a posterior stabilised or medial pivot arthroplasty without patellar resurfacing. Cementless fixation leads to a higher revision rate. If age and computer navigation are evaluated in terms of revision rates, young patients with and without computer navigated arthroplasties failed at the highest rates, distinct from patients >65. However, if failure rates due only to loosening are evaluated, then computer navigation leads to a lower revision rate in the <65 group. This has been interpreted as the protective effect of better component position that only shows up in patients who use the arthroplasty more aggressively. Patient specific instrumentation (PSI) or Individual Designed Instrumentation (IDI) were revised at marginally higher rates than conventional instrumentation. Crosslinked polyethylene appears to be superior at 12 years (CRR= 4%) versus non crosslinked polyethylene (CRR>7%). This is the result of fewer failures due to loosening with crosslinked poly. The superiority of crosslinked poly was greater in the younger, more active patient

The philosophy of cemented total hip arthroplasty (THA) femoral components has become polarised. At one extreme are polished, collarless, tapered devices that are expected to subside; at the other extreme are roughened, non-tapered implants with a collar designed not to subside. Radiostereometric analysis (RSA) allows the accurate measurement of implant movement and has been extensively used for measurement of the in vivo migration of implants. The degree of migration as measured by RSA during the first years after surgery has been shown to correlate with the long-term performance of cemented femoral implants. The purpose of this study was to review the two-year RSA results of two different designs of primary cemented THA stems. Data from two previous prospective RSA trials with two-year follow-up were pooled. The first group included 36 patients who received a Spectron (Smith & Nephew, Memphis, USA) cemented stem. The second group included 13 patients who received an Exeter (Stryker, Mahwah, USA) cemented stem, and 15 patients who received a CPCS (Smith & Nephew, Memphis, USA) cemented stem. All patients underwent RSA examinations shortly post-operation, at 6 weeks, 3 months, 6 months, 1 years, and 2 years. Migration and rotation of the femoral stems was measured at each time point relative to the post-operative exam, and compared between the two groups. There was no difference in age at surgery (Spectron 78 ± 6 years, Exeter/CPCS 77 ± 5 years, p = 0.43), BMI (Spectron and Exeter/CPCS 28 ± 5 kg/m2, p = 0.92), or percentage of male patients (Spectron 23% male, Exeter/CPCS 21% male) between the implant groups. Subsidence was significantly greater (p < 0.0001) at all time points from three months to two years for the Exeter and CPCS stems (0.94 ± 0.39 mm at two years) compared to the Spectron stem (0.05 ± 0.16 mm at two years). There was no significant difference between the stem types for medial-lateral translation (p = 0.07) or anterior-posterior translation (p = 0.49), or for anterior-posterior tilt (p = 0.15), internal-external rotation (p = 0.89), or varus-valgus rotation (p = 0.05). Implant material, design, and surface finish are all factors in the long-term performance of cemented femoral hip implants. In this study, both femoral stem designs had a magnitude of sub-sidence that was within the limits of what is considered to be safe with respect to long-term performance. The continuous subsidence of the Exeter and CPCS stems is consistent with previous reports in the literature

Ultra-high molecular weight polyethylene (UHMWPE) is the sole polymeric material currently used for weight-bearing surfaces in total joint arthroplasty. However, the wear phenomenon of UHMWPE components in knee and hip prostheses after total joint arthroplasty is one of the major restriction factors on the longevity of these implants. In order to minimize the wear of UHMWPE and to improve the longevity of artificial joints, it is necessary to clarify the factors influencing the wear mechanism of UHMWPE. In the microscopic surface observation of the virgin knee prosthesis with anatomical design, various grades of microscopic surface scratches and defects caused by machining and surface finishing processes during manufacture of the component were observed on the surface of the metallic femoral component [Fig. 1] (C. Cho et al, 2009), although the overall surface were finished at smoother level. It is thought that certain levels of the microscopic surface asperities caused by these surface damages in the metallic femoral component might contribute to increasing and/or accelerating wear of the UHMWPE tibial insert. Therefore, it is necessary to clarify quantitatively the influence of the microscopic surface asperities of the metallic components in virgin artificial joints on the wear of UHMWPE components. The primary purpose of this study was to investigate the influence of the microscopic surface asperities of the virgin metallic femoral component on the wear of the UHMWPE tibial insert in the virgin knee prosthesis. In this study, the authors focused on the three-dimensional shape of the microscopic surface asperities as a factor influencing the wear mechanism of the UHMWPE tibial insert. The 3D microscopic surface profile measurement of the virgin metallic femoral component using a laser microscope and reproduction of the femoral component surface using 3D CAD software were performed [Fig. 2] in order to produce idealized 3D finite element models of the microscopic surface asperity of the femoral component based on actual measurement data. Elasto-plastic finite element contact analyses between idealized microscopic surface asperities and UHMWPE were also performed in order to investigate the influence of the three-dimensional shape of the microscopic surface asperities of the virgin metallic femoral component on the wear of the UHMWPE tibial insert. The analytical findings of this study suggest that the aspect ratio and shape ratio [Fig. 3] of the microscopic surface asperity of the virgin metallic femoral component have an important influence on increasing and/or accelerating wear of the UHMWPE tibial insert